Ind. Eng. Chem. Res. 2003, 42, 2381-2386
2381
SEPARATIONS Removal of Carbon Dioxide by Absorption in a Rotating Packed Bed Chia-Chang Lin,† Wen-Tzong Liu,† and Chung-Sung Tan*,‡ Union Chemical Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan, 300 R.O.C., and Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan, 300 R.O.C.
The absorption of carbon dioxide from gases containing 1-10 mol % CO2 in a rotating packed bed was investigated in this study. The aqueous solutions of NaOH, monoethanolamine, and 2-amino-2-methyl-1-propanol were used as the absorbents. The overall volumetric mass-transfer coefficient (KGa) was observed as a function of the rotating speed, gas flow rate, liquid flow rate, absorbent concentration, and CO2 concentration. The obtained results indicated that KGa of a rotating packed bed was comparable to a tower packed with the EX packing, implying a great potential of a rotating packed bed applied to the reduction of the greenhouse gas CO2 from the exhausted gases. Introduction Carbon dioxide is a major greenhouse gas that contributes to the global warming more than 60%.1 It is therefore essential to reduce its emission, especially from power generation plants, to cope with global demand. One of the technical means to achieve the purpose is absorption. Though the absorption of CO2 has been applied to many existing industrial processes such as coal gasification, synthesis-gas production, naturalgas processing, oil refining, and hydrogen manufacture, the cost is still high for the treatment of the exhausted gases of power generation plants because of the fact that a huge volume of the exhausted gas needs to be treated and significant mass-transfer limitations exist in the conventional gas-liquid contactors such as packed tower, spray column, and bubble column. To enhance the mass-transfer rate between gas and liquid, a rotating doughnut-shaped packing device in which liquid and gas are contacted in the presence of a high centrifugal field may be applied. Ramshaw and Mallinson2 had shown that the use of a rotating packed bed (RPB) could enhance distillation and absorption efficiency to a significant extent. This technology has been denoted as higee (high gravity). In a typical RPB operation, liquid flows through the packing element subjected to an acceleration rate of at least 300 m/s2 tuned by the rotating speed. Because a centrifugal acceleration can markedly exceed gravity, there are many benefits. One of them is to reduce the tendency of flooding. Under this circumstance, a RPB can be operated at higher gas and liquid flow rates over packing with a larger surface area (2000-5000 m2/m3) and a higher porosity (90-95%).3 Besides, thinner films and smaller droplets resulting from a large centrifugal acceleration can increase the gas-liquid mass-transfer * To whom correspondence should be addressed. Tel.: 886-3-572-1189. Fax: 886-3-572-1684. E-mail: cstan@ che.nthu.edu.tw. † Industrial Technology Research Institute. ‡ National Tsing Hua University.
rate. Under this situation, a smaller equipment size may be used, leading to a reduction of capital and operating costs. On the basis of these benefits, the operation in a RPB has been proved to be an effective means in distillation, absorption, stripping, deaeration, reactive precipitation, and adsorption.4-17 Munjal et al.5,6 showed a significant improvement of the gas-liquid mass transfer for the absorption of CO2 by an aqueous NaOH solution in a RPB. The gas-liquid effective interfacial area as a function of the rotating speed and liquid flow rate over the packing of glass beads was provided as well. Fowler et al.7 examined the effects of the rotating speed and liquid flow rate on the mass-transfer rate of CO2 into an aqueous diethanolamine solution in a RPB packed with the reticulated material. They found that the mass-transfer rate in a RPB was an order of magnitude higher than that in a packed tower. To verify the applicability of a RPB for the removal of CO2 from the exhausted gas of a power generation plant, more data on CO2 absorption in different absorbents and the effects of operation variables on the performance are required. The common absorbents employed for CO2 absorption are alkanolamines including monoethanolamine (MEA) and 2-amino-2-methyl1-propanol (AMP).18-25 While AMP can overcome the thermodynamic limitation for absorption capacity compared to MEA, its reaction rate with CO2 is lower than that of MEA.18 Under this situation, a mixture of MEA and AMP was suggested to achieve a high absorption capacity and a fast reaction rate.19,20 The objective of this study is to examine the CO2 absorption performance at various operating conditions in a RPB for the absorbents including NaOH, MEA, AMP, and a mixture of MEA and AMP. The measured removal efficiency of CO2 in terms of the overall volumetric mass-transfer coefficient (KGa) was also compared to that in a packed tower. Experimental Section Figure 1 depicts the experimental apparatus for the CO2 absorption. During the operation, the nitrogen gas
10.1021/ie020669+ CCC: $25.00 © 2003 American Chemical Society Published on Web 05/03/2003
2382
Ind. Eng. Chem. Res., Vol. 42, No. 11, 2003
Table 1. Operating Conditions for Various Absorbents in the CO2 Absorption Experiments inlet gas stream inlet liquid stream RPB
CO2 concentration (mol %) gas flow rate (L/min) absorbent concentration (kmol/m3) liquid flow rate (mL/min) rotating speed (rpm)
CO2-NaOH
CO2-MEA
CO2-AMP
CO2-MEA-AMP
1, 10 4.4-13.1 0.2, 0.5, 0.7, 1, 2 42-108 375-1735
1, 8, 10 4.4-13.1 1, 2 42-108 375-1735
8, 10 4.4-13.1 1 42 1735
10 4.4-13.1 MEA (1), AMP (1) 42 1735
Results and Discussion The CO2 removal efficiency of a RPB was assessed by the overall volumetric mass-transfer coefficient in this study. For the chemical absorption of CO2 into hydroxide or amine solutions, besides the liquid-side and gas-side mass-transfer coefficients, the enhancement factor I, defined as the ratio of the liquid mass-transfer coefficient for absorption with and without chemical reaction, is also included in the following expression of KGa:21
1 1 H ) + KGa kGa IkLa Figure 1. Experimental apparatus for CO2 absorption in a RPB.
stream containing CO2 flowed inward from the outer edge of the RPB by a pressure driving force, and the aqueous absorbent was pumped from the storage tank to the inner edge of the RPB via a distributor. The velocity of the aqueous absorbent solution was observed to be high enough to avoid the entrainment in the discharged gas stream. The aqueous absorbent moved outward and left from the outer edge of the RPB via a centrifugal force. Both gas and liquid streams contacted countercurrently in the RPB, in which CO2 in the gas stream was dissolved and reacted with the absorbent in the liquid stream. The gas leaving the RPB was discharged from the top of the RPB, while the CO2-rich aqueous solution was discharged from the side of the RPB. The stainless wire mesh was used as the packing. The RPB had an inner diameter of 7.6 cm, an outer diameter of 16.0 cm, and a height of 2.0 cm. The total volume of the RPB was 311.4 cm3. The packing had a specific surface area of 803 m2/m3 and a void fraction of 0.96. The rotating speed varied from 375 to 1735 rpm, providing a centrifugal acceleration from 91 to 1945 m/s2. Because the flooding was observed to occur at ratios of gas flow rate to liquid flow rate higher than 1000, the variation of the gas and liquid flow rates was therefore under this constraint. The CO2 absorption performances were measured at the operating conditions summarized in Table 1. For all of the runs, a steady-state operation was observed to be reached within 15 min. The CO2 concentrations in the inlet and outlet gas streams were measured by two infrared gas analyzers (LX-720, Ijima Electronics Corp., CO2 ranged from 0 to 0.5%, and Ploytron, Draeger Ltd., CO 2 ranged from 0 to 30%). The absorbent concentrations in the inlet and outlet liquid streams were determined by a titration technique.21 Temperatures in the inlet liquid and gas streams were maintained at around 300 K via two temperature controllers. The operating pressure was at atmospheric pressure.
(1)
For a RPB, the gas-side mass-transfer coefficient (kG) may be estimated by the equation proposed by Onda et al.27
kG ) 2ReG0.7ScG1/3(atdp)2 DGat
(2)
and the liquid-side mass-transfer coefficient (kL) may be calculated by the equation suggested by Tung and Mah26
()
at kLdp ) 0.92ScL1/2ReL1/3 DL a
1/3
GrL1/6
(3)
The gas-liquid interfacial area in eq 3 is evaluated by the correlation proposed by Onda et al.27
[
()
σc a ) 1 - exp -1.45 at σ
0.75
ReL0.1WeL0.2FrL-0.05
]
(4)
From eqs 2-4 and the experimental values of KGa, the enhancement factor I can then be calculated. From the material balance for a RPB, the number of transfer units (NTU) is written as11
NTU )
∫YY Y -1 Y* dY i
(5)
o
The experimental KGa of a RPB can then be determined by the following equation:11,16
KGa )
QG 2
2
πZ(ro - ri )
NTU )
QG 2
2
πZ(ro - ri )
()
ln
Yi Yo
(6)
In the derivation of eq 6, Y* is assumed to be zero because the CO2 content in liquid is zero as a result of the moderately rapid reaction of CO2 with hydroxide and amines.21,28 According to eq 6, a higher KGa represents a better CO2 removal efficiency. To evaluate the CO2 absorption performance of a RPB, the KGa values were measured at different operation variables including the rotating speed, gas flow rate, liquid flow rate, absorbent concentration, and inlet CO2 concentration. The reproducibility tests at almost all of the
Ind. Eng. Chem. Res., Vol. 42, No. 11, 2003 2383
Figure 2. Effect of the rotating speed on KGa for the CO2-NaOH system.
Figure 3. Effect of the gas flow rate on KGa for the CO2-MEA and CO2-AMP systems.
operating conditions were performed in the study. The data on the outlet CO2 concentration and the calculated KGa were observed to be reproduced with a deviation of less than 5%. Figure 2 shows the dependence of KGa on the rotating speed for the use of NaOH as the absorbent under the operations at a liquid flow rate of 42 mL/min, a gas flow rate of 4.4 L/min, and an inlet CO2 concentration of 1 mol %. It is seen that KGa was increased with an increase in the rotating speed in the range from 375 to 1000 rpm, indicating that the mass-transfer resistances were reduced with an increase in the rotating speed. However, when the rotating speed was further increased, only a small effect on KGa was observed. This was probably due to the fact that the extent of reduction in mass-transfer resistances at higher rotating speed was compensated for by a reduction of the retention time that was unfavorable to chemical absorption. Figure 2 also shows that the rotating speed had a larger effect on KGa at lower NaOH concentrations when the rotating speed was less than 1000 rpm. At lower NaOH concentrations, the extent of the chemical absorption of CO2 with NaOH was smaller than that at higher NaOH concentrations. Under this situation, an increase in KGa resulting from an enhancement in the absorption due to a reduction of mass-transfer resistances at high rotating speeds was more pronounced at low NaOH concentrations. A similar dependence of KGa on the rotating speed was also observed for the use of MEA as the absorbent at a CO2 concentration of 1.0 mol %. The observation indicated that a rotating speed higher than 1000 rpm was required to achieve a high CO2 removal efficiency. When MEA and AMP were used as the absorbents under the operations at a liquid flow rate of 42 mL/min, a rotating speed of 1735 rpm, an absorbent concentration of 1 kmol/m3, and the inlet CO2 concentrations of 8 and 10 mol %, Figure 3 shows that there was no significant effect of the gas flow rate on KGa for AMP, indicating that the major mass-transfer resistance lays in the liquid film. This observation was similar to that for a packed tower.29 However, when MEA was used as the absorbent, KGa was found to decrease as the gas flow rate increased. While an increase in the gas flow rate might result in a reduction of the gas-side masstransfer resistances that was beneficial to the CO2 absorption, a reduction of the contact time with an increase in the gas flow rate would hinder the chemical
absorption of CO2. From the obtained results, it was seen that the contact time exhibited more effect on CO2 removal for the CO2-MEA system. It was also seen from Figure 3 that KGa was decreased with an increase in the CO2 concentration. This was attributed to a difficulty to remove more CO2 from the gas stream with a higher CO2 content within the same contact time as the gas stream with a smaller CO2 content. Figure 3 shows that the KGa values for MEA were higher than those for AMP at a given inlet CO2 concentration and gas flow rate, indicating that MEA was more appropriate over AMP to remove CO2 from the flue gases in a RPB. The advantages of using a RPB include an increase in the gas-liquid contact area and a reduction in the gas-liquid mass-transfer resistances. When the gas and liquid flow rates were the same, the contact areas and the liquid- and gas-side mass-transfer coefficients should not be significantly different for the use of MEA and AMP as the absorbents. It is known that the reaction rate of MEA with CO2 is higher than that of AMP;18 the observed results indicated that the reaction rate had a significant effect on the overall mass transfer in a RPB. This can be seen by the estimated enhancement factors I, which were in the ranges of 6.39.1 and 4.1-7.5 for the CO2 concentrations of 8 and 10 mol % for MEA, respectively, and 3.4-4.1 and 2.6-3.1 for the CO2 concentrations of 8 and 10 mol % for AMP, respectively. The results shown in Figure 3 indicate that a proper choice of alkanolamine is essential to achieve a high removal rate of CO2. Figure 4 shows that liquid flow rate had a significant effect on KGa when MEA and NaOH were used as the absorbents at a gas flow rate of 13.1 L/min, a rotating speed of 1735 rpm, an inlet CO2 concentration of 10 mol %, and an absorbent concentration for MEA and NaOH of 2.0 kmol/m3. An increase in the liquid flow rate would reduce the liquid-side mass-transfer resistance and the contact time. The former enhanced KGa, but the latter exhibited a reverse effect. Besides, a higher liquid flow rate would provide more absorbent to absorb CO2, providing a favorable effect on the absorption of CO2. An increase in KGa with an increase in the liquid flow rate, shown in Figure 4, indicates that a decrease in the liquid-side mass-transfer resistance and an increase in the amount of absorbent offer more effects on absorption over a reduction in the contact time. This observation is similar to that for a packed tower.30 Because the variation in the calculated I with an increase in the
2384
Ind. Eng. Chem. Res., Vol. 42, No. 11, 2003 Table 2. Measured KGa Values for the CO2-NaOH, CO2-MEA, and CO2-MEA-AMP Systems absorbent
gas phase CO2 concn, mol % gas flow rate, L/min liquid phase absorbent concn, kmol/m3 liquid flow rate, mL/min operation conditions rotating speed temperature, K KGa, s-1
NaOH
MEA
MEA + AMP
10 4.4-13.1
10 4.4-13.1
10 4.4-13.1
2 42
2 42
1+1 42
1735 1735 1735 300 300 300 0.41-0.53 0.50-0.75 0.41-0.51
Table 3. Comparison of the KGa Values between the RPB and Packed Tower for the CO2-NaOH System packed tower21
Figure 4. Effect of the liquid flow rate on KGa for the CO2-NaOH and CO2-MEA systems. operation conditions pressure, atm temperature, K gas phase CO2 concn, mol % gas flow rate, L/min gas load, m3/m2/h liquid phase NaOH concn, kmol/m3 liquid flow rate, mL/min liquid load, m3/m2/h KGa, s-1 KGa (based on liquid load), s-1 a
Figure 5. Effect of the ratio of the fed CO2 to the fed absorbent on KGa for the CO2-MEA, CO2-NaOH, and CO2-AMP systems.
liquid flow rate was not so significant and much less than that in the calculated kL, the removal of CO2 from the gas stream was believed to be controlled by the liquid-side mass transfer. Figure 5 shows the dependence of KGa on the molar ratio of the fed CO2 to the fed absorbent for the CO2MEA, CO2-NaOH, and CO2-AMP systems. The KGa values for the CO2-MEA and CO2-NaOH systems were found to decrease with an increase of the fed molar ratio and to be more dependent on this ratio. This behavior was also observed for the CO2-NaOH system in a packed tower.30 It is also seen from Figure 5 that the KGa values for the CO2-MEA system were approximately 2-5 times higher than those for the CO2-AMP system. This was because the reaction rate for MEA was faster than that for AMP. From the comparison in KGa, it was suggested to use MEA as the absorbent for CO2 absorption. Table 2 shows KGa for the aqueous solutions containing NaOH, MEA, and a mixture of MEA and AMP at different operating conditions. It is seen that the MEA aqueous solution exhibited the best absorption performance over the solutions containing NaOH and a mixture of MEA and AMP. Table 2 also shows that the KGa values for MEA were at least 20% higher than those for NaOH at the same operating conditions. It is known that the reaction rate in the MEA aqueous solution was less than that in the NaOH aqueous solution;30 a higher
RPB
1 297
1 300
1 4.9-10.4 1044-2196
1 4.4-11.4 38-96
0.2-1.0 23-67 4.9-14.2 1.38-2.41 0.47-1.05a
0.2-1.0 42-108 0.4-0.9 0.38-0.93 0.38-0.93
Calculated based on the correlation proposed by Strigle.28
KGa for MEA was therefore believed to be attributed to a higher gas-liquid interfacial area existed in the RPB. As pointed out by Aroonwilas et al.,30 the MEA aqueous solution possessed a lower surface tension compared to the NaOH aqueous solution. This would lead to a higher gas-liquid interfacial area for the MEA solution. It is also seen from Table 2 that, although the MEA + AMP aqueous solution was not as good as the MEA aqueous solution at the same absorbent concentration, it was comparable to the NaOH aqueous solution. In this study, the measured KGa values in the RPB were also compared to the reported KGa values in a packed tower when the NaOH aqueous solution was used as the absorbent.21 The packed tower was of 110 cm in height and 1.9 cm in diameter, providing a volume nearly identical to that of the present RPB. The EX packing, claiming to provide KGa of about 10-33 times higher than the random packing,21 was used in the packed tower. It is seen from Table 3 that the KGa values in the RPB were about 0.27-0.40 of those in the packed tower. According to the correlation for KGa for the CO2-NaOH system in a packed tower proposed by Strigle,28 KGa depended on a 0.3 power of the liquid load (m3/m2/h). When the liquid loads in the RPB were used to evaluate KGa in the packed tower, Table 3 shows that the KGa values in the RPB were comparable to those in the packed tower. When AMP was used as the absorbent, Table 4 shows that the measured KGa in the RPB was also comparable to that in a packed tower packed with the EX packing reported by Aroonwilas et al.30 According to the KGa correlation for the CO2-AMP system in a packed tower proposed by Aroonwilas and Tontiwachwuthikul,29 KGa varied with 0.5 power of the liquid load. KGa for the packed tower at the same liquid load of the RPB was
Ind. Eng. Chem. Res., Vol. 42, No. 11, 2003 2385 Table 4. Comparison of the KGa Values between the RPB and Packed Tower for the CO2-AMP System packed tower30 operation conditions pressure, atm temperature, K gas phase CO2 concn, mol % gas flow rate, L/min gas load, m3/m2/h liquid phase AMP concn, kmol/m3 liquid flow rate, mL/min liquid load, m3/m2/h KGa, s-1 KGa (based on liquid load), s-1
RPB
1 297
1 300
9.8 4.9-10.4 1044-2196
10 4.4-13.1 38-111
1.1 46 9.7 0.34 0.07a
1 42 0.4 0.14 0.14
a Calculated based on the correlation proposed by Aroonwilas et al.29
also calculated using the proposed correlation. It is seen from Table 4 that KGa in the RPB was 2 times higher than that in the packed tower. On the basis of the comparison in KGa between the RPB and the packed tower for different absorbents and the fact that the EX packing can only be applied to laboratory columns,29 the RPB shows its applicability for the removal of CO2 from an exhausted gas stream. Conclusion The removal of CO2 from a flue gas containing 1-10 mol % of CO2 by absorption in a RPB was studied. The experimental results indicated that a rotating speed higher than 1000 rpm was required to achieve high mass-transfer efficiency. The measured KGa for MEA was observed to be at least 20% higher than that for NaOH, AMP, and a mixture of MEA and AMP, indicating that the MEA aqueous solution was superior to the NaOH, AMP, and MEA + AMP aqueous solutions at the same absorbent concentration for CO2 absorption. From the observed dependence of KGa on the gas flow rate, liquid flow rate, and molar ratio of the fed CO to the fed absorbent, it was concluded that the resistance to mass transfer mainly lies in the liquid film. The comparison of KGa between the RPB and the tower packed with the EX packing for the NaOH and AMP aqueous solutions shows that the KGa values in the RPB were comparable to those in the packed tower, indicating that RPB is an effective gas-liquid contactor for the removal of CO2 from the exhausted gases. Acknowledgment C.-C.L. and W.-T.L. thank the Energy Commission of the Ministry of Economic Affairs, Republic of China, for financial support under Contract 91-D0117. C.-S.T. thank the Industrial Development Bureau, Republic of China, for financial support under Contract 9001020128. Note Added After ASAP Posting This article was released ASAP on 5/3/03 with errors in the legends of Figures 2-5. The correct version was posted on 5/13/03. Nomenclature a ) gas-liquid interfacial area (m2/m3) ac ) centrifugal acceleration (m/s2) at ) total specific surface area of the packing (m2/m3)
DG ) gas diffusivity (m2/s) DL ) liquid diffusivity (cm2/s) g ) gravitational acceleration (cm/s2) H ) Henry’s constant I ) enhancement factor KG ) overall gas-liquid mass-transfer coefficient (s-1) KGa ) overall volumetric mass-transfer coefficient (s-1) kG ) gas-side mass-transfer coefficient (cm/s) kL ) liquid-side mass-transfer coefficient (cm/s) QG ) volumetric flow rate of gas (L/min) ri ) inner radius of a rotating packed bed (cm) ro ) outer radius of a rotating packed bed (cm) VG ) gas superficial velocity (cm/s) VL ) liquid superficial velocity (cm/s) Yi ) mole fraction of CO2 in the inlet gas stream Yo ) mole fractions of CO2 in the outlet gas stream Y* ) gas-phase mole fraction of CO2 in equilibrium with the concentration of CO2 in liquid Z ) height of a rotating packed bed (cm) Greek Letters µG ) gas viscosity (kg/m/s) µL ) liquid viscosity (kg/m/s) FL ) liquid density (kg/m3) σ ) liquid surface tension (N/m) σc ) critical surface tension (N/m) νG ) dynamic gas viscosity (m2/s) νL ) dynamic liquid viscosity (m2/s) Dimensionless Groups FrL ) Froude number (VL2at/g) GrL ) liquid Grashof number (dp2ac/νL2) ReG ) gas Reynolds number (VG/atνG) ReL ) liquid Reynolds number (VL/atνL) ScG ) gas Schmidt number (νG/DG) ScL ) liquid Schmidt number (νL/DL) WeL ) Weber number (VL2FL/atσ)
Literature Cited (1) Halmann, M. M.; Stenberg, M. Greenhouse Gas Carbon Dioxide Mitigation; CRC Press LLC: Boca Raton, FL, 1999. (2) Ramshaw, C.; Mallinson, R. H. Mass Transfer Process. U.S. Patent 4,283,255, 1981. (3) Ramshaw, C. Higee DistillationsAn Example of Process Intensification. Chem. Eng. 1983, 389, 13. (4) Keyvani, M.; Gardner, N. C. Operating Characteristics of Rotating Beds. Chem. Eng. Prog. 1989, 85, 48. (5) Munjal, S.; Dudukovic, M. P.; Ramachandran, P. A. Mass Transfer in Rotating Packed Beds: I. Development of Gas-Liquid and Liquid-Solid Mass-Transfer Coefficients. Chem. Eng. Sci. 1989, 44, 2245. (6) Munjal, S.; Dudukovic, M. P.; Ramachandran, P. A. Mass Transfer in Rotating Packed Beds: II. Development of Gas-Liquid and Liquid-Solid Mass-Transfer Coefficients. Chem. Eng. Sci. 1989, 44, 2257. (7) Fowler, R.; Gendes, K. F.; Nyguard, H. F. Commercial Scale Demonstration of Higee for Bilk CO2 Removal and Gas Dehydration. 21st Annual Offshore Technology Conference, Houston, TX, May 1989. (8) Kumar, M. P.; Rao, D. P. Studies on a High-Gravity GasLiquid Contactor. Ind. Eng. Chem. Res. 1990, 29, 917. (9) Singh, S. P.; Wilson, J. H.; Counce, R. M.; Villiers-Fisher, J. F.; Jennings, H. L.; Lucero, A. J.; Reed, G. D.; Ashworth, R. A.; Elliott, M. G. Removal of Volatile Organic Compounds from Groundwater Using a Rotary air Stripper. Ind. Eng. Chem. Res. 1992, 31, 574. (10) Liu, H. S.; Lin, C. C.; Wu, S. C.; Hsu, H. W. Characteristics of a Rotating Packed Bed. Ind. Eng. Chem. Res. 1996, 35, 3590. (11) Kelleher, T.; Fair, J. R. Distillation Studies in a HighGravity Contactor. Ind. Eng. Chem. Res. 1996, 35, 4646. (12) Guo, F.; Zheng C.; Guo, K.; Feng, Y.; Gardner, N. C. Hydrodynamics and Mass Transfer in Cross-flow Rotating Packed Bed. Chem. Eng. Sci. 1997, 52, 3853.
2386
Ind. Eng. Chem. Res., Vol. 42, No. 11, 2003
(13) Peel, J.; Howarth, C. R.; Ramshaw, C. Process Intensification: Higee Seawater Deaeration. Trans. Inst. Chem. Eng., Part A 1998, 76, 585. (14) Chen, J. F.; Wang, Y. H.; Guo, F.; Wang X. M.; Zheng, C. Synthesis of Nanoparticles with Novel Technology: High-Gravity Reactive Precipitation. Ind. Eng. Chem. Res. 2000, 39, 948. (15) Lin, C. C.; Liu H. S. Adsorption in Centrifugal FieldsBasic Dye Adsorption by Activated Carbon. Ind. Eng. Chem. Res. 2000, 39, 161. (16) Sandilya, P.; Rao, D. P.; Sharma, A.; Biswas, G. Gas-Phase Mass Transfer in a Centrifugal Contactor. Ind. Eng. Chem. Res. 2001, 40, 384. (17) Chen, Y. S.; Liu, H. S. Absorption of VOCs in a Rotating Packed Bed. Ind. Eng. Chem. Res. 2002, 41, 1583. (18) Alper, E. Reaction Mechanism and Kinetics of Aqueous Solutions of 2-Amino-2-methyl-1-propanol and Carbon Dioxide. Ind. Eng. Chem. Res. 1990, 29, 1725. (19) Xiao, J.; Li, C. W.; Li, M. H. Kinetics of Absorption of Carbon Dioxide into Aqueous Solutions of 2-Amino-2-methyl-1propanol + monoethanolamine. Chem. Eng. Sci. 2000, 55, 161. (20) Yeh, J. T.; Pennline, H. W. Study of CO2 Absorption and Desorption in a Packed Column. Energy Fuels 2001, 15, 274. (21) Aroonwilas, A.; Tontiwachwuthikul, P. High-efficiency Structured Packing for CO2 Separation Using 2-Amino-2-methyl1-propanol (AMP). Sep. Purif. Technol. 1997, 12, 67. (22) Mandal, B. P.; Guha, M.; Biswas, A. K. Bandyopadhyay, S. S. Removal of Carbon Dioxide by Absorption in Mixed Amines: Modelling of Absorption in Aqueous MDEA/MEA and AMP/MEA Solutions. Chem. Eng. Sci. 2001, 56, 6217. (23) Tontiwachwuthikul, P.; Meisen, A.; Lim, C. J. CO2 Absorption by NaOH, monoethanolamine and 2-Amino-2-methyl-1-pro-
panol Solutions in a Packed Column. Chem. Eng. Sci. 1992, 47, 381. (24) Li, M. H.; Chang, B. C. Solubilities of Carbon Dioxide in Water + 2-Amino-2-methyl-1-propanol + Monoethanolamine. J. Chem. Eng. Data 1994, 39, 448. (25) Park, S. H.; Lee, K. B.; Hyun, J. C.; Kim, S. H. Correlation and Prediction of the Solubility of Carbon Dioxide in Aqueous Alkanolamine and Mixed Alkanolamine Solutions. Ind. Eng. Chem. Res. 2002, 41, 1658. (26) Tung, T. H.; Mah, R. S. H. Modeling Liquid Mass Transfer in Higee Separation Process. Chem. Eng. Commun. 1985, 39, 147. (27) Onda, K.; Takeuchi, H.; Okumoto, Y. Mass Transfer Coefficient between Gas and Liquid Phases in Packed Columns. J. Chem. Eng. Jpn. 1968, 1, 56. (28) Strigle, R. F., Jr. Random Packing and Packed Towers: Design and Applications; Gulf: Houston, 1987. (29) Aroonwilas, A.; Tontiwachwuthikul, P. Mass-Transfer Coefficient and Correlation for CO2 Absorption into 2-Amino-2methyl-1-propanol (AMP) Using Structured Packings. Ind. Eng. Chem. Res. 1998, 37, 569. (30) Aroonwilas, A.; Veawab, A.; Tontiwachwuthikul, P. Behavior of Mass-Transfer Coefficient of Structured Packings in CO2 Absorbers with Chemical Reactions. Ind. Eng. Chem. Res. 1999, 38, 2045.
Resubmitted for review December 6, 2002 Revised manuscript received April 3, 2003 Accepted April 7, 2003 IE020669+
